Thread: Null Pointer Exception

Well I just started coding in Java with seperate files and classes, and I believe this is an organization problem;

SOOOO I have 3 files:
All have 1 class and methods.

Here's one

public class runprogram {
 
public static void main(String[] args) {
 
runprogram run = new runprogram();
run.runprogram();
}
public void runprogram(){
GetDataMethods f = new GetDataMethods();
Cell cell = new Cell();
cell.assignvalues();
System.out.println(cell.cellarray[4].value);
}
}
 
 
}

Here's the other

public class Cell {
int value;
int xloc;
int yloc;
int possiblevalues[];
Cell[] cellarray = new Cell[81];
//Prints out values of Cell
public void assignvalues(){
	GetDataMethods g = new GetDataMethods();
	Cell one = new Cell();
		int currentnumber = 0;
		for (int row = 0; row <= 8; row++)
		{
		     for(int col = 0; col <= 8; col++)
		     {
		    	 int x = 0;
		    	 currentnumber = g.newboard[row][col];
		    	  one.cellarray[x] = new Cell();
		         System.out.println(one.cellarray[x].value=currentnumber);
		         x++;
 
		     	}
		     }
		}
	 }

And here's my last one
This one has alot more methods I posted only the relevant part of it.

public class GetDataMethods {
	int emptycells[];
	//The Sudoku
    int[][] newboard = {{0,0,0,0,6,0,0,0,9},
                        {0,6,0,0,0,0,3,0,1},
                        {2,0,0,0,0,9,8,0,0},
                        {1,9,6,0,0,2,0,0,8},
                        {0,0,0,3,0,8,0,0,0},
                        {8,0,0,9,0,0,1,7,5},
                        {0,0,1,7,0,0,0,0,4},
                        {6,0,7,0,0,0,0,8,0},
                        {4,0,0,0,9,0,0,0,0}};
//The Possible Values
public int possibilityboard[][];
int value;
}

That's all dandy, however, I get a null pointer exception error if I try using the method assignvalues from Cell class, the file Cell, out side of file Cel.
Any idea what I'm doing wrong?

Basically, why do I get a nullpointer in runprogram?

Not sure if this is the exact solution, but in the loops within assignvalues(), you are always assigning a value to one.cellarray[0] (you reset x to zero with every look). So if you ever try to access one of the other memebers of the cellarray array - such as you are in runprogram - you will get a null pointer exception. Try moving int x = 0 outside the for loops

Never mind I solved it;
Remove the decleration of Cell in the file were the objects are created, then simply in the runprogram declare a new instance of the class, and call the method assignvalues.